Can: Ability and Permission

We use can to talk about ability. The negative of can is cannot (contraction: can’t).

Can you swim?
He can play the guitar.
I can’t open this bottle.Can you meet me tomorrow morning?

We can use can to ask for permission (we also can use may and could).

Can I borrow your dictionary?Can I use your pen?Can I ask you a personal question?

Could is less direct and more polite than can. May is more formal (and some people think it is more ‘correct’) than can or could, but can and could are more common.

When we talk about things that are already permitted or not permitted (e.g. when there is a rule or a law), we use can / can’t (we may aslo use be (not) allowed).

You can’t smoke in this room. (You aren’t allowed to smoke in this room).
You can get married in Great Britain when you are 16. (That’s the law)
The children can go to bed at 9 o’clock, but they can stay up later on Saturdays. (The parents have decided this)